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Old 04-23-2003, 03:05 AM   #16
whansard
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no, demons are everywhere,
and they use modules to ride into your brain.
one more beer, and the demons will be quiet.
oh sorry, you meant daemons.

the Deitel operating systems textbook is pretty good.
you could skim thru that somewhere. i always
thought of the daemon as the dos equivalent of
the tsr. a program that stays in memory waiting
for an event to trigger it taking action, sort of.

I'm sure i'll understand it better after i read the next
chapter of Don Quixote.
 
Old 04-23-2003, 03:12 AM   #17
m0rl0ck
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Quote:
I'm sure i'll understand it better after i read the next

Great post
 
Old 04-23-2003, 03:43 AM   #18
whansard
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are you the morlock from the movie time machine?
if so, the ones from the book or the movie?
are you short, disgusting and pasty looking, and gnaw
at the flesh and bones of little teletubby looking people,
or are you twice the size of human, strong and fast, able
to leap high in the air, and gnaw at the flesh of people
that live on the sides of cliffs?
 
Old 04-23-2003, 04:24 AM   #19
m0rl0ck
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I would be from the :
http://us.imdb.com/Title?0054387
1960 version. Which was my first exposure to the story.
Ive been using the handle for a couple of years.
I can strongly identify with creatures who like regular snacks, have an aversion to sunlight and like technology for technologys sake.
And Im not short
 
Old 04-23-2003, 04:23 PM   #20
jailbait
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A daemon is not a program. The only physical entity for a daemon is a contol block. The rest of what constitutes a daemon is the logic of how the kernel reacts to the information in the daemon control block.

A daemon inherits the permissions of its parent daemon. The only way to create a daemon with different permissions is to take a trip through the security routines. So when you login as user the security routines set up the proper permissions for user. All of the daemons that user starts will have user permissions unless the user goes through security. Thus a user can start bash. In bash the user issues the su command and supplies the password. The resultant daemon is on the user daemon chain, has root permissions, and is running the bash program.

When you start pppd as user (regardless if you use wvdial, kppp, or DoD to start pppd) that pppd has user permissions and runs program ppp. When you start pppd as root that pppd has root permissions and runs program ppp. Thus when a newbie sets his modem up with only root permissions he runs into the problem that he can access the internet through ppp as root but not as user.

There is not a one to one correspondence between daemons and programs. The number of daemons corresponds to the number of programs that can run simultaneously. It is possible for a program to start another program without creating a daemon for it.

I think, but am not sure, that Mozilla calls its subprograms without invoking a daemon. Assuming that's true, then when Mozilla web browser starts its email program that email program does not run in parallel with Mozilla. You have to quit the email program to get back to the browser.

Also ppp can run the transient parts of ppp without setting up another daemon.

ftp programs like gftp or kbear typically start several daemons running
subcomponents of themselves so that they can download continuously while still talking to you through the screen.

---------------------------------------------------------------
I take it, that the daemons are really interprocess-communications facilities

answer: That's one of the functions of daemonic logic.
---------------------------------------------------------------
Actually, I like whansard' answer better than my own.
---------------------------------------------------------------

Another function is access to to the cpu. The kernel runs down the daemon chain and decides who runs next. By switching cpu access rapidly between different daemons the kernel creates the illusion in the human time scale that all of the programs are running simultaneously.
 
Old 04-24-2003, 04:35 AM   #21
JZL240I-U
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Thank you very much for this explanation. Its always good to get a new understanding of things which seemed clear but are, in truth, very different. Thanks again .
 
  


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